PHP实现的限制IP投票程序IP来源分析

if(getenv('HTTP_CLIENT_IP') && strcasecmp(getenv('HTTP_CLIENT_IP'), 'unknown')) {
   $onlineip = getenv('HTTP_CLIENT_IP');
} elseif(getenv('HTTP_X_FORWARDED_FOR') && strcasecmp(getenv('HTTP_X_FORWARDED_FOR'), 'unknown')) {
   $onlineip = getenv('HTTP_X_FORWARDED_FOR');
} elseif(getenv('REMOTE_ADDR') && strcasecmp(getenv('REMOTE_ADDR'), 'unknown')) {
   $onlineip = getenv('REMOTE_ADDR');
} elseif(isset($_SERVER['REMOTE_ADDR']) && $_SERVER['REMOTE_ADDR'] && strcasecmp($_SERVER['REMOTE_ADDR'], 'unknown')) {
   $onlineip = $_SERVER['REMOTE_ADDR'];
}

$head = array();
$head[] = 'GET /i.php HTTP/1.1';
$head[] = 'Host: localhost';
$head[] = 'X-Forwarded-For: 255.255.255.255' ;
$head[] = 'Connection: Close' ;
$head = join("rn",$head) ;
$head .= "rnrn";
$fp = fsockopen('localhost', 80);
fwrite($fp, $head);
$response = array() ;
while($buff = fread($fp, 4096)){
   $response[] = $buff;
}
print join('',$response) ;